Getting started

Requirements#

• Node.js 22
• npm
• A local clone of the JETH repository

JETH is currently pre-release. Use the repository entry point until a versioned jethc package and standalone binary are published.

Install and verify#

npm install
npm run build
npm test

Compile the bundled counter example:

npm run jethc -- examples/Counter.jeth --abi --bin --layout

Write artifacts to a directory:

npm run jethc -- examples/Counter.jeth -o build/

The CLI loads relative imports, handles multi-contract entries, writes complete artifact sets, and provides human or structured output:

jethc <entry.jeth> [options]
  -o, --output <dir>       write artifacts
  --contract <name>        select one contract
  --evm-version <name>     select the EVM target
  --emit <kinds>           select artifact files
  --abi, --bin, --yul      print compiler outputs
  --layout                 print storage layout JSON
  --json                   emit structured JSON
  --config <file>          load project defaults
  --standard-json          read JSON from stdin

Create a contract#

Create Hello.jeth:

class Hello {
  value: u256 = 0n;

  setValue(next: u256): External<void> {
    this.value = next;
  }

  get readValue(): External<u256> {
    return this.value;
  }
}

Compile it:

npm run jethc -- Hello.jeth -o build/

The output directory contains ABI, creation bytecode, runtime bytecode, Yul, storage layout, and versioned metadata. See Compiler, CLI, and tooling for imports, multi-contract selection, configuration, standard JSON, and exit codes.

Read JETH syntax correctly#

• Integer literals use BigInt syntax: 1n, not 1.
• u256 means an EVM uint256, not a JavaScript number.
• A bare class is a contract.
• A bare field is storage.
• A method returning External<T> is externally callable.
• A get method is read-only; the compiler infers pure or view.
• A method without External<T> or Payable<T> is internal.
• Arithmetic is checked unless it is inside unchecked: { ... }.

Next steps#

• Take the language tour.
• Browse progressively larger examples.
• Use the language reference for exact syntax.
• Check SUPPORTED.md before relying on an advanced shape.
• Read security considerations and the compiler correctness model before deploying anything.
• Open BURG at burg.a16k.org to write and compile JETH contracts in the browser with no install required.

JETH language documentationBuilt by @a16k-lab